1. Field of the Invention
The present invention relates generally to a method and apparatus for both humidification and dehumidification through the use of desiccant materials, as well as the automatic regulation of the relative humidity of the air contained in motor powered vehicles (hereinafter "motorized vehicles"), and the efficient automatic elimination and prevention of frost, fog, or condensation on the inside of the window glass of vehicles, and the elimination and prevention of frost in refrigeration units.
2. Description of the Related Art
The invention provides features and benefits by controlling relative humidity in a way not previously available. Automobiles, trucks, vans, trains, boats, ships, military vehicles, aircraft, tractors, motorized recreation vehicles, and various other types of motorized vehicles have previously lacked a successful and economical method or apparatus to automatically monitor and control the relative humidity within the cabin of the vehicle.
Previously produced motorized vehicle environmental systems have been developed to increase or decrease the cabin air temperature, regulate the rate of air flow, filter dust or pollen particles out of the air, defrost/defog the windshield, or reduce cabin noise, but none of the environmental systems have attempted to economically and effectively regulate the relative humidity level of the cabin air. Although the environmental systems in some over the road trucks have utilized water humidification and various dehumidification methods in the past, the systems were either inefficient, unhealthy, or expensive due to their initial installation cost, maintenance requirements, or their high level of energy consumption. There are currently desiccant based dehumidification systems for commercial buildings, however, they do not use the same processes or methods to provide a heat source for regeneration or the same configuration of desiccant wheel that is used as an element of this inventive method and apparatus, and none employ a canister like that shown and claimed.
Traditional refrigeration and freezer units produce frost or condensation within the box or on the evaporator coils when the humidity of the air reaches the saturation point as the air is cooled in the unit. The inherent frost problem restricts the air flow over the coils, creates a frost buildup on the inside of the box, and limits the efficiency of the coils. The current methods of defrosting these types of units use additional energy and utilize expensive apparatus to remove the frost.
In previously manufactured motorized vehicles the relative humidity of the cabin has essentially been unmonitored, unregulated and uncontrolled except through the use of traditional airconditioner evaporator units. The lack of humidity control of the cabin air in motorized vehicle can have a negative effect on safety, comfort, health, and operating efficiency.
In motorized vehicles the need for an efficient and effective way to increase the relative humidity in the cabin to improve the comfort for the occupants has existed for many years. If the motorized vehicle is operating in cold weather without the addition of humidity into the cabin air, the continued use of the heater in combination with the introduction of cool dry fresh air from outside will cause the relative humidity in the cabin to decrease to a point where the occupants may become uncomfortable. Traditional humidification units have experienced many problems due to the need to haul water and health hazards are present from the growth of bacteria, mold and mildew in the system.
In aircraft the problem is compounded because of the long duration of the flight and the extremely low levels of humidity that occurs in aircraft. In most long range commercial aircraft the cabin environmental system is heated by compressed air taken from the compressor section of the turbine engine. Outside air enters the engine air intake, is compressed and thus heated by the compressor section of the engine. Some of the hot compressed air going through the engine is vented off from the engine prior to the air entering the burner section of the engine. The hot air is then forced into the cabin environmental system.
During most flights, the outside air has a low relative humidity before it is heated, and the result of heating the air produces an extremely low relative humidity when the air enters the cabin. Even the moisture given off by evaporation from the occupant's perspiration and from evaporation of moisture out of the occupants lungs is not sufficient to keep the cabin at a high enough relative humidity for it to be comfortable to the occupants. The moisture given off by the occupants and generated from other sources escapes out of the cabin as the stale cabin air is expelled from the cabin. Although the cabin of a commercial aircraft may have the temperature regulated very close to 70.degree. F., the relative humidity can drop to well below 20%.
The CO.sub.2 in the cabin can cause discomfort for the occupants when the CO.sub.2 reaches levels greater than 1000 ppm (parts per million). This high level of CO.sub.2 exist because of the low percentage of new fresh air brought into the cabin as compared to the ratio of old stale air recirculated. The ratio of the fresh air is inadequate to replace enough of the unwanted CO.sub.2. If the environmental system circulates in more fresh air from outside to reduce the ratio of CO.sub.2 and increase the ratio of Oxygen, the resultant air mass would have an even lower relative humidity. This would produce a relative humidity level even lower than the current uncomfortable levels of less than 20%.
These extreme conditions cause the passengers to experience substantial discomfort caused by two factors: 1.) stuffy feeling from poor ventilation of fresh air; and 2.) dryness from extremely low relative humidity. The effects of these two factors manifest in the physiological conditions for the occupants as respiratory irritation, headaches, and fatigue. These same factors also effect the flight crew and impact the safe operation of the aircraft due to the crew member's distraction from the effects of high CO.sub.2 and low relative humidity.
In aircraft design, there has always been strong economic pressure to reduce the operational cost by reducing the cost of fuel. The weight of the aircraft has a direct relationship to the consumption of fuel. For each pound of cargo which must be reduced to off set an additional pound of aircraft weight there is a penalty due to the loss of revenue for the pound of cargo and the additional cost of fuel to transport the extra weight added to the aircraft. If an inventive apparatus is installed in the aircraft, the weight of the apparatus is added to the total air frame weight. Of course, the additional weight of the apparatus will have a long term operational cost disadvantage simply due to the weight of the apparatus installed in the aircraft. The benefits of passenger comfort must off set the cost penalty of initial unit cost and long term operational fuel cost. The cost benefit of lower aircraft weight due to the conditioning of the air in the cabin is a respectable trade-off
It is commonly understood that water is heavier than air. What is not commonly understood is that water vapor is lighter than air. Since the inventive apparatus adds water vapor to the air contained in the cabin the apparatus is actually reducing the weight of the aircraft by reducing the weight of the cabin air. Air is made up of: NITROGEN 78% (NI) with 14.0067 AMU (Atomic Mass Units); OXYGEN 21% (O) with 15.9994 AMU and OTHER GASES 1% which consist of: ARGON 0.9%, CARBON DIOXIDE 0.03% and varying amounts of WATER VAPOR. Since CARBON has an AMU of 12.011 the combined molecule of CARBON DIOXIDE with CARBON: 12.011 and OXYGEN: 15.9994 is actually lighter than OXYGEN alone with 15.9994. This would provide the designer with a marginal incentive to increase the CARBON DIOXIDE content in the air mass of the cabin to reduce the aircraft weight. When OXYGEN 15.9994 is combined with two (2) HYDROGEN 1.00794 AMU atoms the result is a molecule with a much lower weight. Much lighter than NITROGEN, OXYGEN, or CARBON DIOXIDE.
When water vapor is added to the cabin air mass unlike CARBON DIOXIDE the passengers experience more healthful and comfortable breathing and a significantly greater reduction in air mass weight. The evaluation of the apparatus must consider not only to the comfort and safety of the occupants, but also the off set in weight reduction from the water vapor displacement of the heavier cabin air gasses. Many people working with desiccants will refer to removing a given amount of water from an air mass, and the values given may be pounds of water or gallons of water, what they fail to mention is the water vapor removed is replaced by a heavier air mass.
It is not practical for the aircraft designers to simply modify the aircraft environmental systems by adding a conventional liquid humidification apparatus which would increase relative humidity in the cabin air with an atomized spray of water into the vent system to perform the needed humidification. The addition of a water based humidification system would only create a new set of problems. These problems include the added cost of transporting the liquid water, the additional maintenance expense to keep the system clean and operating properly, and health concerns related to bacteria growing in the wet area of the system.
The cabin environmental systems for today's commercial aircraft were designed to use a minimum amount of energy from the engines by simply recirculating more old stale cabin air and adding less fresh air from outside the aircraft. The fresh air from outside is brought into the aircraft by bleeding off heated compressed air from the compressor section of the engine (bleed air). In today's large long haul aircraft cabins, the manufactures have traded off passenger comfort and health for fuel efficiency which has created unhappy passenger with a strong desire for better comfort and a more healthful environmental system.
There is a significant need to develop a method to economically and safely humidify the fresh outside air which is forced into the cabin. If aircraft cabin environmental systems had the capability to increase the humidity in the cabin, this would not only solve the current problem with the existing low level of relative humidity, this would also enable the system designers to increase the ratio of fresh air introduced into the cabin without causing a severely negative impact on the relative humidity level of the cabin air.
For the environmental system to bring more fresh air into the cabin, the designers must consider the following factors, including, but not limited to:
1.) the need to compensate for additional heat from the added fresh air to maintain the cabin temperature of 70.degree..
2.) the effects from a larger volume of fresh air on maintaining the correct level of cabin pressure.
3.) the requirement for additional humidification of the additional fresh air to correct for the lower relative humidity.
Since the aircraft engine compressor system has the capability to provide larger volumes of fresh air that is both heated and compressed the modification to these elements of the existing environmental systems would be minimal. The remaining system deficiency, which is the lack of relative humidity control, would require the incorporation of a new humidification system.
Although aircraft experience the most severe cabin environmental problems related to low relative humidity, all other closed cabin motorized vehicles including but not limited to cars, trucks, busses, boats, military vehicles, trains, etc. experience similar low humidity problems of varying degrees. Many occupants of land motorized vehicles experience discomfort from low relative humidity in the cabin. The operators of overland trucks, individuals spending long duration's of time in automobiles, busses or other motorized vehicles experience discomfort from extremely low relative humidity due to the effect of operating the cabin heater for extended periods.
Just as most motorized vehicles have the need to regulate the temperature for passenger comfort by either increasing or decreasing the environmental air temperature and rate of air flow in the cabin, there is also a need to control the percent of relative humidity of the cabin air to provide an acceptable level of comfort.
Existing motorized vehicles lack an effective dehumidification system, they have three significant reasons why this improvement is needed: 1.) Safety could be enhanced by eliminating windshield fog/frost; 2.) Comfort for the occupants could be improved by controlling the maximum level of relative humidity; and 3.) Efficiency in the operation of the motorized vehicle from a reduction of fuel consumption could be attained due to the reduction of energy consumption of the existing air-conditioning system since the current method of dehumidification expends additional compressor energy on the condensation of moisture on the evaporator coils of the traditional air-conditioner.
Motorized vehicle operation safety is believed to be significantly enhanced by this invention due to the automatic prevention or rapid elimination of visual impairment or obstruction from condensation, fog, or frost on the inside of cabin windows of motorized vehicles (e.g. cars, trucks, boats, helicopters, tractors, trains, military equipment, airplanes, etc.) Motorized vehicles have for years experienced window/windshield condensation under certain environmental conditions. The closed area of the cabin, along with the occupants breathing out moist air, and in some cases rain soaked clothing tends to rapidly produce condensation on the inside of the glass of the windows. Condensation has been known to accumulate during the operation of a motorized vehicle when the inside cabin air temperature and high relative humidity of the cabin combines with the cold window glass to produce windshield fog/frost.
Traditional cabin defrost/defog systems provide the operator with the option to switch to outside air and/or increase the inside cabin temperature to remove the condensation. This method of defrost/defog attempts to eliminate the condensation by introducing outside air with a lower level of humidity and/or change the inside air temperature, or the temperature of the window glass, to avoid having the inside air reach the due point. Another traditional approach, that consumes additional fuel, is using the air-conditioner evaporator to defrost the windshield while the heater is operating to warm the cabin.
The net result of these systems is the occupants must take the necessary actions to attempt to eliminate the condensation, and the comfort of the occupants may also be sacrificed so as to eliminate the condensation. In these situations, safe operation of the motorized vehicle could be jeopardized because the corrective action to eliminate the condensation does not usually begin until the occupant can see the condensation, which is often after the operator's vision is already impaired. The operator must then adjust the environmental controls by attempting to set the climate controls to a setting which will eliminate the condensation. If the operator makes the adjustment incorrectly the window may actually accumulate more condensation and create a more serious unsafe condition, such as when the operators vision through the windshield or other windows is completely blocked by condensation.
There are times when the introduction of outside air is undesirable to the occupants of the cabin, such as when the motorized vehicle is passing through smog, exhaust filled environments, or in the presents of other anxious gases or fumes. Most of the current methods attempting to eliminate condensation are only adaptations to the conventional heating and cooling units and neither of these systems have the distinct capability to effectively control both the cabin relative humidity and temperature. For example, on high humidity days with rain soaked occupants entering the motorized vehicle the systems must rapidly eliminate the condensation from the windshield. As the cabin air mass warms up the moisture from the clothing begins to evaporate into the air as the warmer air mass increases it's capability to hold moisture. The warm moisture saturated air is cooled when it comes in contact with the inside surface of the windshield glass which causes the moisture to form condensation on the surface of the glass. Many environmental control systems of motorized vehicles do not have the capability to immediately eliminate or prevent the formation of condensation on the windshield under these conditions.
Since the definition of environmental air-conditioning is not limited to just cooling when considering occupant comfort, the definition also encompass temperature, air motion, moisture levels, radiant heat levels, dust, various pollutants, sound, and microorganisms when considering the total cabin environment air conditioning. Relative humidity control should be a major element of the overall system design. Although many of the cabin environmental systems in today's motorized vehicles have been improved to include automatic temperature and air volume movement (CFM) control settings, manufactures have not incorporated into climatic control systems the capability to automatically and efficiently increase or decrease the relative humidity level in the cabin.
The human body regulates it's temperature of 98.6.degree. F. during different levels of physical activity. The metabolic rate of an individual is based on the activity level of the individual. The human body tends to be comfortable in a temperature range of 67.degree. F.-to-72.degree. F. in Winter and 73.degree. F.-to-79.degree. F. Summer. With the body continuously giving off heat @ 98.6.degree. F. to the surrounding air mass with 70.degree. F., the body regulates the rate of heat emission to maintain a constant 98.6.degree. F. The body metabolic rate while sleeping is 0.7, while driving a car 1.5, while walking 2.6, and during competitive sports 8.7. The higher the metabolic rate, the more heat the body needs to give off to maintain 98.6.degree. F. The body controls it's temperature by controlling the emission of energy from the body by radiation, by convection to air currents that impinging on the skin or clothing, by conduction of clothing and objects that are contacted, and by evaporation of moisture in the lungs and of sweat from the skin.
Evaporation and convection heat loss are functions of air temperature and velocity. Evaporation is a function, in addition, of relative humidity. Air-conditioning (A/C) cooling units for traditional motorized vehicles primarily use convection heat loss to maintain the comfort for the occupants of the cabin. These A/C cooling units do not have the capability to lower the relative humidity much below the saturation level to enhance the human body's natural cooling effect from evaporation. In the existing motorized vehicles equipped with environmental cooling units, when the occupants wants faster cooling, they must lower the unit's temperature setting, increase the air flow volume to maximum, and set the unit's air flow to recirculate. These settings may increase the body's cooling rate, but they also create an uncomfortable cold clammy feeling for the occupants if the cabin has a high relative humidity. If the relative humidity exceeds 60% the occupants feel wet.
For example, when the temperature is below 70.degree. F. and the relative humidity is in excess of 60% the occupant feels clammy-cold, and with a high relative humidity and the temperature above 77.degree. F. they feel sticky-hot. There are many times when the occupants may be operating the A/C cooling unit because they feel uncomfortable even when the cabin temperature is below 70.degree. F. due to a relative humidity above 60%.
If the environmental control unit had the capability to independently control the relative humidity the occupant would feel comfortable using a smaller volume of cool air and would actually operate the compressor cooling unit less often.
The air-conditioning cooling units in today's motorized vehicles are both mechanical (belt) driven and electrical powered from the engine. The air-conditioner system places an additional load on the engine that decreases the motorized vehicle's acceleration performance and increases the engine's fuel consumption. The lack of efficiency in the air-conditioner equates into higher fuel cost of operating the motorized vehicle and lower performance.
Since today's motorized vehicle's environmental systems lack the capability to lower the relative humidity before the air passes over the cooling coils, the air-conditioner must use additional energy to condense out the moisture when the air has a high relative humidity. The condensing out of the moisture on a high temperature, high humidity day causes the unit to expends approximately 20% to 30% of it energy performing this conversion of water vapor to a liquid. As the air temperature is lowered with a high relative humidity it passes over the cooling coils and the moisture will condense out as the air approaches the dew point. The condensation produced from this cooling can create wet areas within the air-conditioner unit where dangerous bacteria can grow and then spread into other areas of the system or cause the inside of the motorized vehicle to smell like mildew. If the cooling coils are below 32.degree. F. the condensation will form frost on the coils.
Most available units are designed to maintain the cooling coil temperature at about 35.degree. F. to eliminate the build up of ice on the coils. The air-conditioning unit's air cooling output is limited by it's ability to lower the air's temperature because of this minimum temperature limit on the coils of 35.degree. F. If the relative humidity in the air passing over the coils could be lowered, the dew point of the moisture in the air would be lower and the condensation would not form until the air reached a much lower temperature, or if the relative humidity is low enough it may never form frost when the air passes over these cold coils.
Since the units are limited by the 35.degree. F. coil temperature the cold air output of the unit cannot be lower than the temperature of the coils without a frost build up, therefore, the systems are designed to put out larger volumes of air (Cubic Feet/Minute) to accomplish the necessary cabin air cooling. Moving larger volumes (CFM) of air requires greater energy consumption.
The currents systems are noisy and the blast of cold air on the occupants produce an unpleasant cabin environment. Since these systems produce cold moist air the occupants will set the temperature lower because the occupant's own body is not benefiting by the potential cooling effect from the body's natural evaporation that could be gained with a lower relative humidity of the air stream entering the cabin. Since the air-conditioners lack the capability to lower the relative humidity without operating the compressor the occupants will turn on the air-conditioner more often because they feel uncomfortable. The occupants could be perfectly comfortable with a higher cabin temperature if the relative humidity were lower.
In summary, high fuel consumption in the current environmental systems is believed to be largely the result of: 1.) having to move more CFM of air to accomplish the necessary cooling; 2.) minimum cooling coil temperature of 35.degree. F.; 3.) the occupants will set the desired temperature lower than necessary for comfort due to high relative humidity; 4.)the occupants will use the unit more often for comfort; and, 5.) cooling moist air requires more energy than cooling dry air;.
Substantial savings in fuel consumption of motorized vehicles could be obtained if cabin environmental units could efficiently lower the relative humidity to a comfortable level in the cabin air.
Conventional systems do not have the capability to perform both the humidification and dehumidification function utilizing the same elements of their apparatus. Many times the environmental system is operating the heater while the air-conditioning cooling is operating to eliminate windshield condensation; and few if any, vehicles have the capability to effectively dehumidify the cabin air.
Many motorized vehicles and trailers pulled by motorized vehicles have refrigeration or freezer units to keep the contents of the trailer or truck cold or below freezing. Most freezer equipment has been designed to go through a defrost cycle to eliminate the frost. The defrost cycles consist of a heating cycle in most cases to melt the frost that has formed on the coils. These defrost cycles are inefficient due to the heating and re-cooling required to perform the defrosting. Some units have duel coils to allow one to defrost while the other coil is cooling. None of these units has the capability to regulate the relative humidity other than through the current methods of using the cold evaporator coils to condense out moisture, or allow the build up of frost and then melt the frost thereby allowing the water to drained to the outside of the unit. A large amount of energy is expended by these units to remove frost and moisture.